1. Field of the Invention
The present invention relates to an imaging lens device. More specifically, the present invention relates to an imaging lens device provided with a compact and high-zoom-magnification zoom lens system suitable for digital input and output apparatuses such as digital cameras and a cameras incorporated in or externally attached to a personal computer, a mobile computer, a mobile telephone or the like. Moreover, the present invention relates to digital input and output apparatuses having an imaging lens device provided with a compact and high-zoom-magnification zoom lens system.
2. Description of the Related Art
In recent years, with the spread of personal computers and the like, digital still cameras, digital video cameras and the like (hereinafter, referred to as digital cameras) capable of easily capturing image information into digital apparatuses have been spreading among private users. It is expected that such digital cameras will more and more spread as image information input apparatuses in the future.
The image quality of a digital camera generally depends on the number of pixels of a solid-state image sensing device such as a CCD (charge coupled device). At present, consumer model digital cameras have as many as more than one million pixels, and their image quality is approaching that of film-based cameras. Since it is desired that these consumer model digital cameras also perform zooming of images, particularly optical zooming that hardly causes image quality degradation, a small-size and high-zoom-magnification digital camera zoom lens system satisfying high image quality has been required in recent years.
For size reduction of imaging devices (imaging optical systems), as disclosed in U.S. Pat. No. 5,448,319, European Patent No. 0906587 and U.S. Pat. No. 6,104,432, the size in the direction of the optical axis of the optical system is further reduced by bending the optical system by inserting a prism or a reflecting mirror between lenses. U.S. Pat. No. 5,448,319 discloses a fixed focal length lens system of which optical axis is bent once for vehicle-mounted monitor cameras. European Patent No. 0906587 discloses a fixed focal length lens system of which optical axis is bent twice. U.S. Pat. No. 6,104,432 discloses a zoom lens system of which optical axis is bent once.
However, in U.S. Pat. No. 5,448,319 and European Patent No. 0906587, although size reduction is attained by bending the optical path, the disclosed optical systems are fixed focal length lens systems and not high-zoom-magnification zoom lens systems satisfying high image quality.
In the optical system disclosed in U.S. Pat. No. 6,104,432, although the size in the direction of the depth is reduced by bending the optical axis of the zoom lens system once, the size in the vertical direction is not reduced. To further reduce the size of this optical system, it is considered to further bend the optical axis. However, it is impossible to further bend the optical axis of this optical system. In a high-zoom-magnification zoom lens system with a magnification of approximately 5×, since the number of lens elements is large and the movement amounts of the movable lens units are large, the overall length is large, so that the camera body on which such a zoom lens system is mounted is increased in size. When the overall length of the optical system is forcibly reduced, the sensitivity to errors increases, so that manufacture errors significantly affect the optical performance. When the overall length of the optical system is reduced by increasing the number of lens units that are movable during zooming, the lens barrel structure is complicated, so that the camera body is increased in size. To bend the optical path for size reduction of a high-image quality and high-zoom-magnification zoom lens system, it is necessary to consider the disposition of the movable lens units and the resultant lens barrel structure.